The International Cessna^® 170 Association

Dear fellow members:

My TSO'd King KY 97a secondary comm is in for service and if it is beyond repair, I was wondering if a non-TSO'd radio would be legal in my 170?

Today at the avionics shop, the tech slid a new non-TSO'd radio in the rack just to run some tests and it worked great. The tech said that the non-TSO'd radios are physically identical to the TSO'd radios.

Since the non-TSO'd radios cost less, I'm guessing that they aren't legal...seems to be the way these things always work out.

Thanks,

Curt

Your radios do NOT need to be TSO'd. Many aircraft are flying around with King KX-170B radios as well as other non-TSO'd radios and it is perfectly legal. However, your radio must not be on the "Unacceptable radio" list. These radios became illegal on Jan. 1, 1997. This is do to FCC regulations and has nothing to do with TSO. Narco radios are listed under National Aeronautical Corp.

http://wireless.fcc.gov/aviation/badlst.html

Karl:

Thank you. Your input is very helpful. If I end up needing another radio, I'll certainly consider the lower cost of the non-TSO'd units.

Curt

lowNslow wrote:Your radios do NOT need to be TSO'd. Many aircraft are flying around with King KX-170B radios as well as other non-TSO'd radios and it is perfectly legal. However, your radio must not be on the "Unacceptable radio" list. These radios became illegal on Jan. 1, 1997. This is do to FCC regulations and has nothing to do with TSO. Narco radios are listed under National Aeronautical Corp.

http://wireless.fcc.gov/aviation/badlst.html

It's generally a simple matter to determine whether or not your older radio may be continue to me utilized as a transmitter: If it can transmit on 25 kHz spacing it is probably OK. (Example: 123.47 or 123.475) If it cannot select 25 kHz spacing, you should contact your avionics shop to determine the legality of using that transmitter.
Here's the problem: As more precise spacing between channels (frequencies) has developed... many older radios no longer are capable of transmitting without "splashing" over onto adjacent channels/frequencies. This causes interference/blockage/squealing on adjacent channels/frequencies. (If I am transmitting on my old Bendix RT-241 on 122.8 at my local Unicom... I am also "splashing" over and transmitting on the adjacent 122.77/122.775, 122.82/122.825 and also perhaps on still other frequencies that may be in-use at Center to control IFR aircraft! I could be blocking important radio transmissions that are critical to safety. (I actually experienced this when I purchased a Beech Baron with airline-type Gold-Crown radios.... while ferrying the airplane home and communicating with another aircraft on 122.9, I was warned by ATC to stop transmitting on an adjacent frequency or they would be filing a violation against me!) (They were using 122.925 and ATC switched over to 122.9 expressley for the purpose of transmitting to me and giving me a serious warning! I never dreamed that ATC would use a frequency so close to a common mulitcom frequency... but they made me turn it off and throw that radio in the trash!)
This is a serious matter.

Non TSO'd radios are perfectly okay for non commericial aircraft. If you rent out or use your aircraft for flight training/passenger-cargo hauling for profit, you must have TSO'd radios. Doesn't have a thing to do with frequency spacing. That's an old/older radio problem. FCC website has the info on acceptable and unacceptable radios due to freq spacing.
http://wireless.fcc.gov/aviation/badlst.html (unacceptable)
http://wireless.fcc.gov/aviation/goodlst.html (acceptable)
If your radio appears on both list it's okay. Hey I don't write this stuff I just read what the FCC puts out.
FCC license GROL # PG-GB-040835 is mine.

I was not addressing the TSO question in my prior post. (And non TSO'd radios can be just fine in aircraft that are rented out and/or used in some commercial operations. The type of operation does not in itself always determine whether or not installed equipment must be TSO'd.)

TSO'd equipment is required when other equipment installations require it for continued certification purposes. An example might be, when a new nav/com radio is installed in an existing GPS installation in an aircraft, for which IFR approaches will be conducted using an autopilot. TSO will contribute assurance that no interference between various installed equipment occurs. Not only is the GPS already required to meet TSO in order to interface with the autopilot,... the autopilot TSO may also make that requirement. (You wouldn't want a transmission from a non-TSO'd radio to cause the autopilot to suddenly pitch down during an approach.)

Additional factors may make TSO demands on some replacement equipment. But generally, a private aircraft in personal use does not require TSO'd radios.